Arterial pressure is the force applied by blood on arterial walls. In order to measure such a pressure, the force unit applied by blood is divided by the arterial wall area unit and the resulting measure is the pressure unit, for instance mmHg or pascals.
Arterial blood force is the pressure applied by blood to the arterial wall, and the measure results from the blood pressure unit multiplied by the arterial segment wall area unit. Its units are dynes or Newtons.
Cardiac cycle is the set of events related to the blood flow that must occur from the beginning of a heartbeat to the beginning of the next one. Every heartbeat includes two main stages in ventricles: The ventricle systole and diastole. The term diastole means muscle relaxation. Throughout the cardiac cycle, blood pressure increases and decreases in heart and arterial system. The variation of pressure in arteries has two stages: the systolic blood pressure time which is short and a longer time corresponding to the diastolic blood pressure.
Arterial cycle is the unit for the variation of repetitive physical properties of the artery depending on time, which consists of the events of the blood flow and arterial wall in a higher blood movement period referred to as systolic period and a lower blood movement period referred to as diastolic. As shown in the dissertation “EL CICLO ARTERIAL” Universidad Autónoma de Tamaulipas, Mexico, Facultad de Medicina de Tampico to obtain the Master of Science degree with specialization in Medical Urgencies, from Jesús Bustillos Cepeda, which has not been published due to the prosecution of the subject patent application. With respect to the amount of pressure of the artery during systolic and diastolic stages, the systolic blood pressure is the highest pressure from the two stages and has blood flow all throughout the stage; while the diastolic blood pressure is the lowest pressure from the two stages and its blood flow does not always last the full arterial cycle diastolic time.
To obliterate: To obstruct or close a conduit or cavity.
Measurement of diastolic arterial pressure through arterial obliteration by applying a gradual external contact force: It is the action of applying a gradual external contact force until obliterating an artery to measure the force applied by the blood on the arterial wall in the diastolic period.
To clear: To remove something that obstructs another thing.
Measurement of diastolic arterial pressure through arterial clearing by removing the gradual external contact force: It is the action of removing the gradual external contact force until an artery has been cleared in order to measure the force applied by the blood on the arterial wall in the diastolic period.
Measurable artery: Arterial segment which is used to know the measurement of a magnitude.
Measurable artery: In the present invention; an arterial segment used to know the pressure measurement applied by blood on its wall area unit.
Parameter: is the numerical value or fixed data that is considered in the study or analysis of a certain issue.
In the present application, a parameter is a sample of blood flow and arterial wall expressions without being affected by the external force applied. Such values shall be taken into consideration to calculate systolic and diastolic arterial pressure.
Arterial pressure can be measured in an invasive (direct) manner, which is not relevant for this document, or in a non-invasive (indirect) manner.
Measuring diastolic and systolic arterial pressure using an indirect method is essential for this invention and in the state of the art such measuring is performed using the auscultatory method and the oscillometric method, which have their origin, description and scientific foundations on the following historical facts:
Auscultatory Method (Classic Method):
1896: Development of blood pressure measurement indirect method by Von Riva Rocci Recklinghaus who, literally, states: “ . . . the instrument I have developed measures in a manometric fashion the force that is required to stop the pulse wave progression; sphigmomanometry is performed in one of the major branches of the aorta artery, on the humeral artery, which is a direct continuation of the axillary one, in such a manner that the measurement estimates the full load in a point that is very near to the aorta artery, almost inside the same . . . ”1905: The Von Riva Rocci Recklinghaus technique is improved by the addition of auscultation by a Russian surgeon, Nikolai Sergeyevich Korotkoff who, in his dissertation from the Imperial Academy of Military Medicine in Saint Petersburg in 1905, described the sounds heard using a stethoscope placed on the brachial artery under the Von Riva Rocci Recklinghaus cuff during slow deflation, which literally states in a translation from Russian to English language: “ . . . The cuff of Riva—Rocci is placed on the middle third of the upper arm; the pressure within the cuff is quickly raised up to complete cessation of circulation below the cuff. Then, letting the mercury of the manometer fall one listens to the artery just below the cuff with a children's stethoscope. At first no sounds are heard. With the falling of the mercury in the manometer down to a certain height, the first short tones appear; their appearance indicates the passage of part of the pulse wave under the cuff. It follows that the manometric figure at which the first tone appears corresponds to the maximal pressure. With the further fall of the mercury in the manometer one hears the systolic compression murmurs, which pass again into tones (second). Finally, all sounds disappear. The time of the cessation of sounds indicates the free passage of the pulse wave; in other words at the moment of the disappearance of the sounds the minimal blood pressure within the artery predominates over the pressure in the cuff. It follows that the manometric figures at this time correspond to the minimal blood pressure . . . ”Oscillometric Method:1940 Report of the “self-monitoring” concept and its differences with arterial pressure measurements in the doctor's office (Ayman and Goldshine); 1969 Theoretical demonstration of the oscillometric principle (Posey); 1970 Oscillometry clinical applications (MAPA and AMPA). The oscillometric method is used by most non-invasive automated devices. One limb and its vasculature are compressed in one arm by an inflatable condensation cuff. The simplified measurement principle from the oscillometric method is an amplitude measurement of pressure change in the cuff. As the cuff is inflated onr systolic pressure, the amplitude suddenly increases with pulse breaks through occlusion. This is very close to the systolic pressure. When cuff pressure is reduced, the amplitude pulse increase reaches its maximum threshold and then quickly decreases. The diastolic arterial pressure index is taken when this transition begins. Therefore, systolic and diastolic blood pressure is obtained by identifying the region in which there is, respectively, a rapid increase and a reduction in pulse amplitude. Medium arterial pressure is found in the point of the maximum oscillation.
The instruments that are used to observe arterial expressions being depicted by Korotkoff are the stethoscope, pressure sensor, flow sensor and sphygmomanometer with respect to a manometer, in order to determine arterial pressure. In the methods to measure arterial pressure in the state of the art, measurements are performed by observing the expressions that have been previously depicted by Korotkoff in his dissertation. In the state of the art, arterial pressure measurement is ruled by the Korotkoff's method in which, in order to measure arterial pressure, the following steps are followed: 1) The humeral artery is pressed against the humeral bone through the pneumatic cuff; 2) the time in which the pressure being applied closes the arterial flow is detected; 3) once the artery has been occluded, pulse wave expressions are not observed anymore and pressure is applied beyond the occlusion point; 4) then the cuff pressure is reduced by opening the valve that is found in the insufflation bulb; 5) the pulsatile blood flow reappearance through the partially compressed artery results in Korotkoff's sounds (sounds resulting from the arterial pulse wave produced by systolic pressure when arriving to the partially occluded artery); 6) when the first Korotkoff's sound appears, the pressure level at the cuff indicates systolic arterial pressure, also referred to as “Korotkoff sounds' stage I” and which is the maximum pressure generated by the pulse wave during each cardiac cycle; 7) the pressure applied on the artery continues to be reduced, permanent disappearance of Korotkoff's sounds indicates diastolic arterial pressure magnitude, since laminar blood flow restoration in the artery eliminates Korotkoff's sounds, such sound elimination being observed in stage V from Korotkoff's sounds classification.
The five Korotkoff's sounds are classified by stages in the state of the art:
Stage I: indicates that vessel pressure has exceeded external pressure, being a sudden, loud and progressively intense sound corresponding to systolic arterial pressure.
Stage II: the sound is more intense, lengthy, and more clear.
Stage III: the sound continues to be loud and clear, although a murmur begins to be perceived which indicates its proximate disappearance.
Stage IV: there is a sudden loss of sound intensity, which becomes markedly muffled with a continuous murmur; it is sometimes the last thing which is heard and some authors determine diastolic blood pressure in this stage.
Stage V: sound fully disappears when laminar flow is restored. World Health Organization advises that diastolic arterial pressure shall be measured in this stage.
The oscillometric procedure is the measure based on amplitude oscillations resulting from the pressure change inside a force application device. It also depends on Korotkoff's observations to measure arterial pressure, as its name indicates, the method uses the oscillometer, which is an electronic device based on the pulse wave analysis. In such oscillometric method, the individual's arm is compressed by an inflatable condensation cuff, such that the measurement is based on the pressure change amplitude in the cuff. Therefore, when such a cuff is inflated on systolic pressure, the amplitude suddenly increases with pulse rest periods through occlusion, that is, very near to systolic pressure. When cuff pressure decreases, amplitude pulse increase reaches a maximum threshold and then rapidly decreases. Diastolic pressure index is taken when this transition begins. Therefore, systolic and diastolic blood pressures result from identifying the region in which there is a sudden increase and then a decrease in the amplitude of systolic pulses.
According to background scientific evidence, it is seen that, by using the procedures and devices in the state of the art to indirectly measure arterial blood pressure, it is only possible to measure systolic arterial pressure in two points: The first one is blood systolic pressure when overcoming the force applied to the measurable artery and the second one is the pressure in the cuff when it is not able anymore to affect blood systolic pressure. The latter pressure is referred to as diastolic arterial pressure, which is not accurate. Measuring systolic arterial pressure using Korotkoff's method does determine in fact systolic arterial pressure, but including the error corresponding to pressure overload that heartbeats occurring after occlusion produced in the occluded artery. The second systolic pressure phenomenon, which is mistakenly known as diastolic arterial pressure, is determined by using the state of the art methods and instruments. Such a measurement consists of measuring the pressure applied by the cuff to the arm at the time in which Korotkoff's sounds disappear, since the pressure applied using the cuff decreases to a point at which it does not affect anymore the blood flow of the major systolic pulse wave, allowing that the turbulent systolic arterial blood flow becomes a laminar flow and thus it does not result in expressions (Korotkoff's sounds). In spite of being clearly a phenomenon of the systolic arterial pressure, it has been usually determined that this measurement corresponds to diastolic arterial pressure.
In the state of the art, diastolic arterial pressure is defined as “the lowest value from both arterial blood pressures values, which corresponds to arterial blood pressure when heart is in a diastolic or resting state”.
According to the above, it may be seen that, in the state of the art, procedures and devices to measure arterial blood pressure in a non-invasive manner, exhibit a major disadvantage: although they try to measure indirect diastolic arterial pressure, they do not manage to do so. Therefore, the state of the art exhibits a scientific gap, since there are no methods or instruments measuring diastolic arterial pressure using an indirect method! This is due to the fact that “What exists in the state of the art to measure diastolic arterial pressure are methods and instruments to measure the minor external contact force applied using a device on the artery at the time in which systolic arterial pressure is not able anymore to produce Korotkoff's sounds resulting from arterial wall vibrations and blood flow turbulences corresponding to systolic arterial pressure”. Along with the above, by using the instruments and procedures found in the state of the art, the only way of measuring diastolic arterial pressure is by using an invasive method (intra-arterial catheter).
The present invention aims to solve some of the following problems in the auscultatory method (classic method): the indirect Von Riva Rocci Recklinghaus' method to measure arterial blood force that is literally stated as follows: “the instrument I have developed measures in a manometric fashion the force that is required to stop the pulse wave progression; sphigmomanometry is performed in one of the major branches of the aorta artery, on the humeral artery, which is a direct continuation of the axillary one, in such a manner that the measurement estimates the full load in a point that is very near to the aorta artery, almost inside the same” . . . .
Comments on Von Riva Rocci's principle: Under normal conditions, the artery exhibits a flow having a pressure and force determined before ventricular ejection, referred to as diastolic pressure. This pressure is ignored by Von Riva Rocci in his description! Such an arterial blood diastolic pressure is suddenly interrupted by the blood volume which is ejected by the heart to the artery in a short period of time, resulting in a higher blood pressure and force which provokes an expansion of the artery which is referred to as arterial pulse wave. Von Riva Rocci Recklinghaus' technological and scientific contribution is an instrument and procedure to manometrically measure the force required to stop the pulse wave progression, that is, the systolic force or pressure, since this is the one generating such a wave.
The above results in the problematic fact that Riva Rocci did not determined the measurement of diastolic arterial pressure by using an indirect method.
Later on, Von Riva Rocci Recklinghaus' technique is improved with the addition of auscultation made by the Russian surgeon Nikolai Sergeyevich Korotkoff, who states the following in its dissertation: “ . . . With the further fall of the mercury in the manometer one hears the systolic compression murmurs, which pass again into tones (in second place). Finally, all sounds disappear. The time of the cessation of sounds indicates the free passage of the pulse wave; that is, at the moment of the disappearance of the sounds the minimal arterial pressure within the artery predominates over the pressure in the cuff. It follows that the manometric reading at this time corresponds to the minimal arterial pressure”.
Korotkoff refers to the artery producing short tones that their aspect indicates part of the pulse wave, when he states “ . . . the manometric reading continues . . . ”, he means that the deflation phenomenon continues and thus the decrease of the pressure applied to the arm by the cuff, as well as that the first tone that appears as a full tone compared to the preceding ones corresponds to the maximum pressure. As seen in the description, maximum pressure results from measuring the external force with the appearance of the first full tone after an actual occlusion and force release resulting from deflation. This technique does not consider the phenomenon that the time on which occlusion is observed includes several cardiac cycles with no tone expression and that every cardiac cycle produces a volume defined by the upper end of humeral artery, which shall allow the fluid passage for the irrigation of the arm, forearm, and hand. Nevertheless, due to the arterial occlusion produced by the cuff due to preventing blood flow passage, volume and pressure are increased in the artery segment located before the artery segment being occluded. This provokes that, when measuring external force guided by the appearance of Korotkoff's first tone, blood pressure magnitude is altered by blood overload due to ventricular ejections occurred after the artery is occluded. The following problem results from the above: how to measure systolic arterial pressure using an indirect method without affecting pressure overload, resulting in ventricular ejections after the artery is occluded?
When describing tones to determine diastolic pressure using an indirect method, Nikolai Sergeyevich Korotkoff states “ . . . With the further fall of the mercury in the manometer one hears the systolic compression murmurs, which pass again into tones (in second place). Finally, all sounds disappear. The time of the cessation of sounds indicates the free passage of the pulse wave; that is, at the moment of the disappearance of the sounds the minimal arterial pressure within the artery predominates over the pressure in the cuff. It follows that the manometric reading at this time corresponds to the minimal arterial pressure”.
And he is right when he states that the sounds disappearing at the end due to cuff deflation are systolic sounds, since pulse is the effect produced by the expansion of the artery as a result of ventricle ejection during cardiac systole. The force applied by the cuff results from reducing the volume in a concentric direction and the highest and lowest forces to be measured in the artery are in an eccentric direction. When the external force occludes the artery and occlusion is progressively released by deflation, the force generating the lowest volume in the artery shall not be affected anymore and finally when the external force applied by deflation falls even more it shall not affect anymore the highest or systolic force, which will emit the last tones depicted by Korotkoff. When tones disappear, diastolic arterial pressure is determined based on arterial expressions due to the relationship between the cuff force and the artery with systolic arterial pressure, and not diastolic arterial pressure actual value!
The above shows that, as it is natural, the lowest or diastolic pressure measurement using Korotkoff's method is made based on systolic arterial pressure effects.
The following problem arises from the above: how to measure diastolic arterial pressure with an indirect method based on its effects and not on the effects resulting from systolic arterial pressure?